The invention concerns brushless d.c. motors the winding of which comprises at least one pair of wound conductors, the conductor pair carrying two current pulses per 360.degree.-el. of rotor rotation, one current pulse being carried by one wound conductor of the pair, the other by the other conductor of the pair, the two wound conductors being connectable to an electrical source, alternately, via respective controllable semiconductor power-carrying elements, such as power transistors that are of conductivity types opposite to or complementary to each other, this occurring under the control of rotor position sensor(s). In this well known motor-circuit configuration, the first conductor of the pair is at one end connected to a first terminal of the source and at its other end is connectable to the second terminal of the source via the associated power-carrying element; similarly, the second conductor of the pair is at one end connected to the second terminal of the source, the other end of the second conductor being connectable to the first terminal of the source via its associated power-carrying element.
More particularly, the present invention concerns a certain version of the above well known motor-circuit configuration, in which version the two conductors of the pair exhibit a.c. voltage coupling, at least at the ends thereof that are connected to the associated controllable semiconductor powercarrying elements.
A motor of such type has been disclosed in West German published patent application ("Offenlengungsschrift") DE-OS No. 30 10 435 and in corresponding U.S. pat. No. 4,374,347 issued Feb. 15, 1983. The two-pulse motor therein illustrated has an extraordinarily simple construction, and the insulation of the two conductors is with such motor less stressed than with other motors, so that the insulation has a higher lifetime.